Professor Abigail Robinson will be giving a lecture at a nearby university, and Chief Inspector Armand Gamache is asked to provide security for it. He discovers an agenda so repulsive that he begs the university to cancel the lecture. They refuse, citing academic freedom, and accuse Gamache of censorship and intellectual cowardice. Before long, Professor Robinson’s views start seeping into conversations so that truth and fact, reality and delusion, are so confused it’s nearly impossible to tell them apart. When a murder is committed, it falls to Gamache, his second-in-command Jean-Guy Beauvoir and their team to investigate the crime, as well as this extraordinary popular delusion. And the madness of crowds.